The present disclosure relates to a developing device used for a copier, a printer, a facsimile, a multifunctional peripheral thereof, and the like, and to an image forming apparatus including the same.
There is known a developing device having a structure in which two transport paths extending close to each other in parallel are disposed for circulating and agitating developing powder, and the developing powder is circulated in the two transport paths by agitating members disposed in the individual transport paths. In this developing device, partition walls are opened to form communicating portions on both ends in a longitudinal direction of the two transport paths so that the developing powder circulates in the two transport paths. The developing powder is transported by the agitating member in the longitudinal direction in the transport path. In order to transport the developing powder to the other transport path, it is necessary to transport the developing powder in the communicating portion in a direction perpendicular to the transport direction in the transport path. When the transport direction of the developing powder is largely changed in the communicating portion in this way, the developing powder may stagnate in the communicating portion.
Therefore, there is known a developing device to resolve the stagnation of the developing powder in the communicating portion. The developing device includes communicating portions opening both ends in the longitudinal direction of the neighboring first and second transport paths, and agitating members disposed in the transport paths for agitating the developing powder to transport the same in the transport paths in the longitudinal direction. The agitating member includes a helical screw disposed on a rotation shaft portion, and a rectangular flat plate paddle disposed to the rotation shaft portion to be opposed to the communicating portion. When the screw rotates, the developing powder is transported in the transport path in the longitudinal direction, and the developing powder is transported from the transport path to the communicating portion by rotation of the paddle. By disposing the paddle to the agitating member in this way, stagnation of the developing powder in the communicating portion is resolved.
However, in the above-mentioned developing device, when the developing powder such as magnetic toner having a relatively low fluidity is agitated and is transported in the transport path in the longitudinal direction, the developing powder may be coagulated by frictional heat between the agitating member and the developing powder. When the developing powder is transported from one of the transport paths to the other transport path via the communicating portion by rotation of the paddle, the coagulated developing powder may adhere to the paddle, or the coagulated developing powder may adhere to the side end surface of the paddle formed in a rectangular shape. As a result, there is an inconvenience that the developing powder can be hardly transported smoothly in the communicating portion.